Firearm accessories are typically mounted to rails, sometimes known as sliding rails, prismatic rails, or accessory rails, which are coupled to the top or side profiles of the firearm. Some conventional rails include both rear and front sights and, for some, either or both of the rear sight and the front sight are retractable. See, for example, U.S. Patent Publication No. 2003/0127085; U.S. Pat. Nos. 5,142,806; 5,590,484; and 6,499,245; and German Patent No. DE 199 05 405.
Retractable rear sights are particularly known in the field of hunting in drop barrel weapons, particular three-barreled guns, which are usually manufactured via an expensive manual labor process. Typically, these foldable rear sights retract automatically when the weapon is set for firing rounds of buckshot to create a continuous surface with the sliding rail and then unfold again automatically when switching to rounds of bullets to provide sighting abilities. In addition, weapons shooting rounds of buckshot often also have a hinged, rough shotgun sight covering its rigidly mounted rifle sight. However, a front sight remains visible under all circumstances and protrudes over the front end of the sliding rail. Consequently, the sliding rail, which is constructed as a straight sliding rail or as a hollow rail, may primarily facilitate the aiming of the weapon when either fleeting rounds of bullets or rounds of buckshot are used. However, though movable in a retractable manner, these sights, once in the unfolded position, may not be properly aligned with and for the marksman.
Other weapons, such as machine-produced modern automatic pistols, usually include a carrying strap mounted on the top side of the weapon, which provides a top layer of protection or cover for the operating elements of the weapon. The carrying strap also forms a carrying handle in which an optical or mechanical sight is embedded or to which such a sight is mounted. Because the axis of the bore (i.e., center axis of the barrel) generally runs through the base plate of the shoulder support to minimize recoil action, the sight of the weapon must be attached at a considerable distance above the barrel so that the marksman occupies a natural position when firing the weapon. That is, the sight, which is the standard sight of the weapon, may be embedded in the carrying handle and may project far enough above the barrel of the weapon so that the line of sight is at an ideal distance above the weapon. Consequently, the additional mounting of a special aiming device (e.g., a sniper scope, telescopic sight, laser sight etc.) to the weapon, often results in an inaccurate location of the sighting line because the standard sight already occupies the ideal location.
Because the carrying straps of most automatic firearms, such as pistols, are removable, it would be possible to replace the carrying strap with a special aiming device. However, this would then omit the standard sight, which is disadvantageous because the special aiming device usually cannot be used as universally as the standard sight. In addition, though additional prismatic rails to which the special aiming devices are mounted, may be removed with repeating weapons, pistols, machine guns, automatic pistols, etc., other devices (e.g., search lights) can be detachably mounted in such a way that they do not block the line of sight.
In the case of weapons for snipers, guns and hunting rifles it is customary either to leave the standard sight off in the first place or to cover it up with the telescopic sight so that the standard sight can only be used when the telescopic sight has been taken off. In addition, there are telescopic sight assemblies for hunting weapons under which one can see through the standard sight; however, as indicated above with automatic pistols, this results in non-ideally positioned sights, i.e., the two lines of sight lie on top of one another so that, at best, only one can be optimal.
A hunting rifle with a narrow prism rail for holding the telescopic sight must be tested again each time the telescopic sight is taken off and put back on. In the case of wider sight rails this is not necessary, in particular in the case of the so-called “Picatinny rail.” Thus, in this case, it is expedient to remove the special aiming device, in particular in military action, each time (e.g., after the action when the special sighting device is not required) to protect the weapon and/or the special sighting device from damage. This means that a standard weapon is generally equipped with its standard sight so that the weapon may be aimed even after the removal of the special aiming device.
However, when conditions such as, for example, environmental conditions change, it may be practical to remove an accessory like the special aiming device whenever it has become impractical (e.g., a night sight during the daytime). Then it is necessary that the standard sight is tested (i.e., adjusted) and that its line of sight is at the correct height, if possible. This is also true for other types of weapons and other types of accessories. For example, a laser sight used with a pistol may be practical during twilight but senseless if, for example, the batteries are dead or the weapon is being used on a sunny day in the open. However, though the inclusion of retractable sights greater decreases the need for gross realignment of the site while accessories are either mounted or removed, the retractable sights, once in the unfolded position, may, nonetheless be misaligned with and for the marksman.